All i can doubt is the adapter is not supported. I got mini HDMI to VGA adapter from an electronic shop (It doesnt have a brand but its a Chinese made). After connecting, everything worked like a charm!

I guess NUC should not be having any problems. Try different adapters.

Well, today I received a bona fide mini-HDMI to regular HDMI cable and attached to my ASUS VW246H monitor. Unfortunately nothing's changed. The system still behaves as if it's working, but just no video signal at all.

Is there a way to "factory reset" the NUC so that it goes back to the state it was in when I first did see video, the first time I turned it on? My guess is that it's got some video setting set that won't let it rediscover the current monitor and until I clear it I'm screwed. Note I did try cycling the monitor inputs using the button on it for that, no luck. It keeps saying "no video signal".

I solved the problem and I'm leaving my findings here for others who experience the same problem.

- I had to give up on the micro to regular HDMI cable. During my web searching I believe I read that LCD monitors don't have the necessary signal converters to use HDMI directly like an HDMI TV can. I wish I could find the reference so I may be incorrect on this. But in any case, HDMI to my PC compatible LCD monitor was a complete failure for me.

- To solve it, I got an Display Port to DVI cable. I simply plugged the Display Port end into the NUC and the DVI end into my LCD monitor and it worked great the first time and every time after that.

NOTE. THE FOLLOWING IS SHEER SPECULATION:

The only thing I can figure is that the very first time I turned on the NUC the BIOS or some other persistent setting was in a state that had it put out a signal that worked with the original VGA output adapter I tried at the very start. Once it rebooted and something got saved, that path never worked again. So the moral is, to get the NUC working with an LCD monitor the safest path is to use the Display Port connected to an LCD monitor's DVI input. Fortunately the d54250WYKH NUC like mine has a headphone out jack so unlike other older NUC's I still can get sound output easily.